Vehicle exhaust treatment systems are used to reduce undesired emissions, such as oxides of nitrogen (NOx) and particulate matter (e.g., soot) output by the vehicle engine. The vehicle exhaust systems typically include a particulate filter (“PF”), which traps the soot from the exhaust gas generated by the engine. The PF may include one or more filter substrates that define a plurality of apertures, through which the exhaust gas must flow. The particulate matter collects on the filter substrate as the exhaust gas flows through the apertures. A regeneration operation may be performed to burn away the collected particulate matter and regenerate the PF. The regeneration operation heats the particulate filter to a combustion temperature sufficient to combust (i.e., burn) the collected particulate matter.
One or more regeneration events for initiating the regeneration operation may be determined according to a soot model. The soot model may be used to estimate and predict soot accumulation on the particulate filter, which may indicate the desirability to perform the regeneration operation. However, changes in the temperature at which an engine operates can cause appreciable variations in quantities of soot carried in the engine exhaust stream. Conventional exhaust treatment systems have attempted to compensate for variations in the quantity of soot loading during low operating conditions, such as urban driving condition, by applying a single non-varying (i.e., static) continuously regenerating trap (CRT) correction factor to the soot model based on NOx levels in the exhaust gas.